diff options
Diffstat (limited to 'sysdeps/x86_64/multiarch/memcmpeq-avx2.S')
| -rw-r--r-- | sysdeps/x86_64/multiarch/memcmpeq-avx2.S | 309 |
1 files changed, 305 insertions, 4 deletions
diff --git a/sysdeps/x86_64/multiarch/memcmpeq-avx2.S b/sysdeps/x86_64/multiarch/memcmpeq-avx2.S index 0181ea0d8d..0bf59fb8fa 100644 --- a/sysdeps/x86_64/multiarch/memcmpeq-avx2.S +++ b/sysdeps/x86_64/multiarch/memcmpeq-avx2.S @@ -16,8 +16,309 @@ License along with the GNU C Library; if not, see <https://www.gnu.org/licenses/>. */ -#ifndef MEMCMP -# define MEMCMP __memcmpeq_avx2 -#endif +#if IS_IN (libc) + +/* __memcmpeq is implemented as: + 1. Use ymm vector compares when possible. The only case where + vector compares is not possible for when size < VEC_SIZE + and loading from either s1 or s2 would cause a page cross. + 2. Use xmm vector compare when size >= 8 bytes. + 3. Optimistically compare up to first 4 * VEC_SIZE one at a + to check for early mismatches. Only do this if its guranteed the + work is not wasted. + 4. If size is 8 * VEC_SIZE or less, unroll the loop. + 5. Compare 4 * VEC_SIZE at a time with the aligned first memory + area. + 6. Use 2 vector compares when size is 2 * VEC_SIZE or less. + 7. Use 4 vector compares when size is 4 * VEC_SIZE or less. + 8. Use 8 vector compares when size is 8 * VEC_SIZE or less. */ + +# include <sysdep.h> + +# ifndef MEMCMPEQ +# define MEMCMPEQ __memcmpeq_avx2 +# endif + +# define VPCMPEQ vpcmpeqb + +# ifndef VZEROUPPER +# define VZEROUPPER vzeroupper +# endif + +# ifndef SECTION +# define SECTION(p) p##.avx +# endif + +# define VEC_SIZE 32 +# define PAGE_SIZE 4096 + + .section SECTION(.text), "ax", @progbits +ENTRY_P2ALIGN (MEMCMPEQ, 6) +# ifdef __ILP32__ + /* Clear the upper 32 bits. */ + movl %edx, %edx +# endif + cmp $VEC_SIZE, %RDX_LP + jb L(less_vec) + + /* From VEC to 2 * VEC. No branch when size == VEC_SIZE. */ + vmovdqu (%rsi), %ymm1 + VPCMPEQ (%rdi), %ymm1, %ymm1 + vpmovmskb %ymm1, %eax + incl %eax + jnz L(return_neq0) + cmpq $(VEC_SIZE * 2), %rdx + jbe L(last_1x_vec) + + /* Check second VEC no matter what. */ + vmovdqu VEC_SIZE(%rsi), %ymm2 + VPCMPEQ VEC_SIZE(%rdi), %ymm2, %ymm2 + vpmovmskb %ymm2, %eax + /* If all 4 VEC where equal eax will be all 1s so incl will overflow + and set zero flag. */ + incl %eax + jnz L(return_neq0) + + /* Less than 4 * VEC. */ + cmpq $(VEC_SIZE * 4), %rdx + jbe L(last_2x_vec) + + /* Check third and fourth VEC no matter what. */ + vmovdqu (VEC_SIZE * 2)(%rsi), %ymm3 + VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm3, %ymm3 + vpmovmskb %ymm3, %eax + incl %eax + jnz L(return_neq0) + + vmovdqu (VEC_SIZE * 3)(%rsi), %ymm4 + VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm4, %ymm4 + vpmovmskb %ymm4, %eax + incl %eax + jnz L(return_neq0) + + /* Go to 4x VEC loop. */ + cmpq $(VEC_SIZE * 8), %rdx + ja L(more_8x_vec) + + /* Handle remainder of size = 4 * VEC + 1 to 8 * VEC without any + branches. */ + + /* Adjust rsi and rdi to avoid indexed address mode. This end up + saving a 16 bytes of code, prevents unlamination, and bottlenecks in + the AGU. */ + addq %rdx, %rsi + vmovdqu -(VEC_SIZE * 4)(%rsi), %ymm1 + vmovdqu -(VEC_SIZE * 3)(%rsi), %ymm2 + addq %rdx, %rdi + + VPCMPEQ -(VEC_SIZE * 4)(%rdi), %ymm1, %ymm1 + VPCMPEQ -(VEC_SIZE * 3)(%rdi), %ymm2, %ymm2 + + vmovdqu -(VEC_SIZE * 2)(%rsi), %ymm3 + VPCMPEQ -(VEC_SIZE * 2)(%rdi), %ymm3, %ymm3 + vmovdqu -VEC_SIZE(%rsi), %ymm4 + VPCMPEQ -VEC_SIZE(%rdi), %ymm4, %ymm4 + + /* Reduce VEC0 - VEC4. */ + vpand %ymm1, %ymm2, %ymm2 + vpand %ymm3, %ymm4, %ymm4 + vpand %ymm2, %ymm4, %ymm4 + vpmovmskb %ymm4, %eax + incl %eax +L(return_neq0): +L(return_vzeroupper): + ZERO_UPPER_VEC_REGISTERS_RETURN -#include "memcmp-avx2-movbe.S" + /* NB: p2align 5 here will ensure the L(loop_4x_vec) is also 32 byte + aligned. */ + .p2align 5 +L(less_vec): + /* Check if one or less char. This is necessary for size = 0 but is + also faster for size = 1. */ + cmpl $1, %edx + jbe L(one_or_less) + + /* Check if loading one VEC from either s1 or s2 could cause a page + cross. This can have false positives but is by far the fastest + method. */ + movl %edi, %eax + orl %esi, %eax + andl $(PAGE_SIZE - 1), %eax + cmpl $(PAGE_SIZE - VEC_SIZE), %eax + jg L(page_cross_less_vec) + + /* No page cross possible. */ + vmovdqu (%rsi), %ymm2 + VPCMPEQ (%rdi), %ymm2, %ymm2 + vpmovmskb %ymm2, %eax + incl %eax + /* Result will be zero if s1 and s2 match. Otherwise first set bit + will be first mismatch. */ + bzhil %edx, %eax, %eax + VZEROUPPER_RETURN + + /* Relatively cold but placing close to L(less_vec) for 2 byte jump + encoding. */ + .p2align 4 +L(one_or_less): + jb L(zero) + movzbl (%rsi), %ecx + movzbl (%rdi), %eax + subl %ecx, %eax + /* No ymm register was touched. */ + ret + /* Within the same 16 byte block is L(one_or_less). */ +L(zero): + xorl %eax, %eax + ret + + .p2align 4 +L(last_1x_vec): + vmovdqu -(VEC_SIZE * 1)(%rsi, %rdx), %ymm1 + VPCMPEQ -(VEC_SIZE * 1)(%rdi, %rdx), %ymm1, %ymm1 + vpmovmskb %ymm1, %eax + incl %eax + VZEROUPPER_RETURN + + .p2align 4 +L(last_2x_vec): + vmovdqu -(VEC_SIZE * 2)(%rsi, %rdx), %ymm1 + VPCMPEQ -(VEC_SIZE * 2)(%rdi, %rdx), %ymm1, %ymm1 + vmovdqu -(VEC_SIZE * 1)(%rsi, %rdx), %ymm2 + VPCMPEQ -(VEC_SIZE * 1)(%rdi, %rdx), %ymm2, %ymm2 + vpand %ymm1, %ymm2, %ymm2 + vpmovmskb %ymm2, %eax + incl %eax + VZEROUPPER_RETURN + + .p2align 4 +L(more_8x_vec): + /* Set end of s1 in rdx. */ + leaq -(VEC_SIZE * 4)(%rdi, %rdx), %rdx + /* rsi stores s2 - s1. This allows loop to only update one pointer. + */ + subq %rdi, %rsi + /* Align s1 pointer. */ + andq $-VEC_SIZE, %rdi + /* Adjust because first 4x vec where check already. */ + subq $-(VEC_SIZE * 4), %rdi + .p2align 4 +L(loop_4x_vec): + /* rsi has s2 - s1 so get correct address by adding s1 (in rdi). */ + vmovdqu (%rsi, %rdi), %ymm1 + VPCMPEQ (%rdi), %ymm1, %ymm1 + + vmovdqu VEC_SIZE(%rsi, %rdi), %ymm2 + VPCMPEQ VEC_SIZE(%rdi), %ymm2, %ymm2 + + vmovdqu (VEC_SIZE * 2)(%rsi, %rdi), %ymm3 + VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm3, %ymm3 + + vmovdqu (VEC_SIZE * 3)(%rsi, %rdi), %ymm4 + VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm4, %ymm4 + + vpand %ymm1, %ymm2, %ymm2 + vpand %ymm3, %ymm4, %ymm4 + vpand %ymm2, %ymm4, %ymm4 + vpmovmskb %ymm4, %eax + incl %eax + jnz L(return_neq1) + subq $-(VEC_SIZE * 4), %rdi + /* Check if s1 pointer at end. */ + cmpq %rdx, %rdi + jb L(loop_4x_vec) + + vmovdqu (VEC_SIZE * 3)(%rsi, %rdx), %ymm4 + VPCMPEQ (VEC_SIZE * 3)(%rdx), %ymm4, %ymm4 + subq %rdx, %rdi + /* rdi has 4 * VEC_SIZE - remaining length. */ + cmpl $(VEC_SIZE * 3), %edi + jae L(8x_last_1x_vec) + /* Load regardless of branch. */ + vmovdqu (VEC_SIZE * 2)(%rsi, %rdx), %ymm3 + VPCMPEQ (VEC_SIZE * 2)(%rdx), %ymm3, %ymm3 + cmpl $(VEC_SIZE * 2), %edi + jae L(8x_last_2x_vec) + /* Check last 4 VEC. */ + vmovdqu VEC_SIZE(%rsi, %rdx), %ymm1 + VPCMPEQ VEC_SIZE(%rdx), %ymm1, %ymm1 + + vmovdqu (%rsi, %rdx), %ymm2 + VPCMPEQ (%rdx), %ymm2, %ymm2 + + vpand %ymm3, %ymm4, %ymm4 + vpand %ymm1, %ymm2, %ymm3 +L(8x_last_2x_vec): + vpand %ymm3, %ymm4, %ymm4 +L(8x_last_1x_vec): + vpmovmskb %ymm4, %eax + /* Restore s1 pointer to rdi. */ + incl %eax +L(return_neq1): + VZEROUPPER_RETURN + + /* Relatively cold case as page cross are unexpected. */ + .p2align 4 +L(page_cross_less_vec): + cmpl $16, %edx + jae L(between_16_31) + cmpl $8, %edx + ja L(between_9_15) + cmpl $4, %edx + jb L(between_2_3) + /* From 4 to 8 bytes. No branch when size == 4. */ + movl (%rdi), %eax + subl (%rsi), %eax + movl -4(%rdi, %rdx), %ecx + movl -4(%rsi, %rdx), %edi + subl %edi, %ecx + orl %ecx, %eax + ret + + .p2align 4,, 8 +L(between_16_31): + /* From 16 to 31 bytes. No branch when size == 16. */ + + /* Safe to use xmm[0, 15] as no vzeroupper is needed so RTM safe. + */ + vmovdqu (%rsi), %xmm1 + vpcmpeqb (%rdi), %xmm1, %xmm1 + vmovdqu -16(%rsi, %rdx), %xmm2 + vpcmpeqb -16(%rdi, %rdx), %xmm2, %xmm2 + vpand %xmm1, %xmm2, %xmm2 + vpmovmskb %xmm2, %eax + notw %ax + /* No ymm register was touched. */ + ret + + .p2align 4,, 8 +L(between_9_15): + /* From 9 to 15 bytes. */ + movq (%rdi), %rax + subq (%rsi), %rax + movq -8(%rdi, %rdx), %rcx + movq -8(%rsi, %rdx), %rdi + subq %rdi, %rcx + orq %rcx, %rax + /* edx is guranteed to be a non-zero int. */ + cmovnz %edx, %eax + ret + + /* Don't align. This is cold and aligning here will cause code + to spill into next cache line. */ +L(between_2_3): + /* From 2 to 3 bytes. No branch when size == 2. */ + movzwl (%rdi), %eax + movzwl (%rsi), %ecx + subl %ecx, %eax + movzbl -1(%rdi, %rdx), %ecx + /* All machines that support evex will insert a "merging uop" + avoiding any serious partial register stalls. */ + subb -1(%rsi, %rdx), %cl + orl %ecx, %eax + /* No ymm register was touched. */ + ret + + /* 2 Bytes from next cache line. */ +END (MEMCMPEQ) +#endif |